OCTOWS2811 -> 30 or 60 pixels/m recommendation?

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hunter10

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Greetings pjrc community!

I looked into LED matrices last year, but the prices and libraries kept me from getting involved. I recently found Paul's octows2811 library, and it's a game changer!

I've got a teensy3 I've been using to play around with small lasers for awhile, and I'm going to jump in and order 10m of ws2811's from china.
First 2 things I'm going to try out are a 8x30 (or 8x60) matrix, and an infinity mirror, and hopefully gain some inspiration along the way.

Im looking for thoughts on the 30/m strip vs 60/m for that matrix. For scrolling text, is it important to go with the 60/m? With the 60 having half the horizontal spacing of the 30, would you then decrease the vertical spacing between the strips as well?
I'll be playing with these indoors, so the increased brightness of 60/m isn't a benefit.


I see 30/m are C$8.50 per meter, 60/m are C$12.00 (Canadian dollars) on Aliexpress.
 
It's really unfortunately nobody makes 90/m. That would be really nice for getting the LEDs closer, but not so close (as in the 144/m) that you don't get a well spaced grid when the strips are laid down side-by-side.

For scrolling text, definitely go for the 60/m. Only 30/m is too sparse.
 
Agreed. I tried with 30/m and it was not a good effect. 60/m is what I have used for the scrolling text led hat, using just a 50cm length of display and it reads OK so long as you are not too close. Also, the text is wrapped around the hat and so you only get to see a small portion of it, but the brain still makes it out OK.

mortonkopf
 
mortonkopf said:
Agreed. I tried with 30/m and it was not a good effect. 60/m is what I have used for the scrolling text led hat, using just a 50cm length of display and it reads OK so long as you are not too close. Also, the text is wrapped around the hat and so you only get to see a small portion of it, but the brain still makes it out OK.

mortonkopf
Click to expand...

Definitely saw your top hat in my research! Looked great.


Just to be certain, as theres several variations, I should be looking for: 5V DC, cuttable every 1 LED, one of WS2811/2812/2812B (same thing).
I've seen it on alibaba in 4m rolls, 5m rolls, and recently saw a 5.5m per roll. Any differences there?

Will be placing orders tonight, pretty damn excited!
 
Don't make the same mistake I did... buy some extra for spares.

I had a few LEDs die. The failure mode seems to be weak solder joints that get stressed when the LEDs heat up and cause the strip to flex or bend slightly. Sometime the "bad" LED can be temporarily fixed by pressing on it. I mounted mine pretty securely to a board using double-sticky tape. In hindsight, a less rigid mounting that allows the strip to bend naturally might have been better. But really, I only use it for occasional demos, and for developing OctoWS2811, so it's not a big deal.
 
The 144led/m came from chenled and the 60led/m came from greeled, i think that both were described as ws2811. The 144led/m were of low build quality on one of the strips, the 60led/m had no issues (but I only bought low volumes). I had to pay customs duty on both sets (I live in UK).

as far as the difference between WS2811 and WS2812B, I can't help as I have never ordered any ws2812. There are some posts online about this that might help, but its not something that I have looked into yet.
 
I know you've already settled on 60/m, but I felt it was worth pointing out the obvious: it really depends on the final "resolution", size, and viewing distance. a 16x64 matrix will look like a 16x64 matrix (assuming equal h/v spacing), but the spacing on the 30/m strips will be double that of the 60/m (and therefore lead to twice as big of a display at half the brightness). A good diffusing material can help mask the pixel gaps as well.

I used 30/m, but I'm not displaying video. I'm not displaying text either, but I have played around with doing so and it looks just fine on a 41x60 matrix (or 82x60, w/ two rows) with decent light diffusion in front of the LEDs. I could not have afforded to do this project with 60 led/m, as I was covering an entire ceiling. 60/m would not only have doubled my cost of LEDs, but it would have put the power requirements far out of reach.

Just food for thought for anyone else reading the thread :)
 
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